It is known to use a sensor to detect when a bearing-supported shaft begins non-concentric rotation, due to bearing wear, and comes into contact with a surface, and to generate an electrical signal corresponding to the sensed contact. An example of such a sensing arrangement is disclosed in U.S. Pat. No. 5,224,835. Other patents which describe bearing wear or failure sensing arrangements are: U.S. Pat. Nos. 6,314,788; 6,271,761; and 6,237,877.
The prior art bearing wear sensing arrangements have one or more of the drawbacks of being relatively complicated or expensive.